COCCOSTEUS 131 
pass from the region of hinder plates of the body armour 
to that of the tip of the tail. This is seen to be bordered 
by neural and hzmal processes, V, H, which in size and 
character are somewhat comparable with those of Protop- 
terus or Pleuracanthus. The dorsal fin presents a meta- 
meral series of supporting cartilages (radial and basal, DR, 
DB). The basal supports of each pelvic fin have become 
compressed into a flattened plate, VB. Pelvic fins were 
present, but there have as yet been found no traces of 
pectoral appendages. In Dinichthys Newberry believed 
that a pectoral fin spine was present, and that this fin was 
Fig. 130. — The Devonian Arthrodiran, Coccosteus decipiens, Ag. X 4. Old Red 
Sandstone, Scotland. (Side view, restored; slightly modified, after SMITH WoopD- 
WARD.) 
A, Articulation of head with trunk. D#Z. Cartilaginous basals of dorsal fin. 
DR. Cartilaginous radials of dorsal fin. A. Hzemal arch and spine. MC. Mu- 
cous canals. NV. Neural arch and spine. U. Median unpaired plate of hinder 
ventral region. V2. Basals of ventral fin. V2. Radials of ventral fin, 
probably Siluroid-like (p. 171), but this view has not been 
_ confirmed. 
The head of Coccosteus was clearly flattened, with 
orbits and nasal openings near its anterior margin; it 
was roofed by a stout buckler of closely fitted dermal 
plates (Fig. 131), whose outer surface was tuberculate, 
_ enamelled, and furrowed by sensory grooves, WC. The 
_ arrangement of the dermal plates of Coccosteus was early 
_ (1861) compared by Huxley with that of recent Siluroids, 
